[Synthesis]
The general procedure for the synthesis of (S)-2-amino-3-(4-benzoylphenyl)propionic acid from L-phenylalanine and benzoyl chloride was as follows: in a reaction tube fitted with a screw cap and polytetrafluoroethylene (PTFE)-faced rubber lining, L-phenylalanine (16.5 mg, 0.1 mmol) was added followed by trifluoromethanesulfonic acid (0.5 mL). After the solution was homogenized, benzoyl chloride (8 eq.) was added slowly at 0 °C. The reaction mixture was stirred at room temperature for 12 hours. Upon completion of the reaction, the mixture was poured into a mixture of cold water and ethyl acetate. The organic layer was separated, washed with saturated sodium chloride solution, dried over anhydrous magnesium sulfate and filtered. The filtrate was concentrated and the residue was purified by silica gel column chromatography (eluent ratio ethyl acetate:methanol:water=8:1:0.5) to give a colorless amorphous product (7.5 mg, 28% yield, 98% enantiomeric excess value). The structure of the product was confirmed by 1H-NMR (CD3OD): δ 7.76 (d, 2H, J=8.6 Hz, Ar), 7.75 (d, 2H, J=8.6 Hz, Ar), 7.64 (t, 1H, J=7.4 Hz, Ar), 7.52 (t, 2H, J=7.4 Hz, Ar), 7.47 (d, 2H, J=8.0 Hz, Ar ), 3.83(m, 1H, Hα), 3.35(m, 1H, Hβ), 3.09(m, 1H, Hβ). |